It has been found that the porosity of a bank note increases from new due to abrasion and other kinds of wear caused by the normal daily handling of the note.
The porosity of a bank note is particularly important if the bank note is to be used in an ATM which utilizes vacuum techniques to pick a bank note from a currency cassette within the ATM for dispensing to a customer.
If the porosity of the bank note is such that a suction device used to pick the bank note from a currency cassette is unable to engage the bank note securely, the ATM will fail. Such a failure will result in an increase in the downtime of the ATM in which the ATM is unable to dispense cash to or receive cash from a customer.